Advances in technology have resulted in smaller and more powerful computing devices. For example, there currently exist a variety of portable personal computing devices, including wireless computing devices, such as portable wireless telephones, personal digital assistants (PDAs), and paging devices that are small, lightweight, and easily carried by users. More specifically, portable wireless telephones, such as cellular telephones and internet protocol (IP) telephones, can communicate voice and data packets over wireless networks. Further, many such wireless telephones include other types of devices that are incorporated therein. For example, a wireless telephone can also include a digital still camera, a digital video camera, a digital recorder, and an audio file player. Also, wireless telephones can process executable instructions, including software applications, such as a web browser application, that can be used to access the Internet. As such, these wireless telephones can include significant computing capabilities.
Typically, the computing capabilities of such devices may be provided by multiple semiconductor devices, where each semiconductor device includes a die having specialized circuitry. Two or more dies, such as a die with modem circuitry and a die with communications circuitry, may be stacked on a substrate in a package. One typical method of stacking dies uses a conductive spacer layer between a host die and a stacking die. The conductive spacer layer electrically connects to the bottom of the stacking die but does not electrically connect to the top of the host die due to a protective passivation layer on the surface of the host die. Wire bonds are used to connect the staked die, the conductive spacer layer, and the host die to conductive pads on the package substrate. However, this stacking method can be difficult and expensive due to increased assembly process steps and packaging costs. In addition, typical spacer materials, such as a conductive aluminum surface layer on a silicon spacer, do not fasten well to packaging materials such as die attachment material and mold compound.